Naphthazarin Derivatives in the Light of Intra- and Intermolecular Forces

Our long-term investigations have been devoted the characterization of intramolecular hydrogen bonds in cyclic compounds. Our previous work covers naphthazarin, the parent compound of two systems discussed in the current work: 2,3-dimethylnaphthazarin (1) and 2,3-dimethoxy-6-methylnaphthazarin (2). Intramolecular hydrogen bonds and substituent effects in these compounds were analyzed on the basis of Density Functional Theory (DFT), Møller-Plesset second-order perturbation theory (MP2), Coupled Clusters with Singles and Doubles (CCSD) and Car-Parrinello Molecular Dynamics (CPMD). The simulations were carried out in the gas and crystalline phases. The nuclear quantum effects were incorporated a posteriori using the snapshots taken from ab initio trajectories. Further, they were used to solve a vibrational Schrödinger equation. The proton reaction path was studied using B3LYP, ωB97XD and PBE functionals with a 6-311++G(2d,2p) basis set. Two energy minima (deep and shallow) were found, indicating that the proton transfer phenomena could occur in the electronic ground state. Next, the electronic structure and topology were examined in the molecular and proton transferred (PT) forms. The Atoms In Molecules (AIM) theory was employed for this purpose. It was found that the hydrogen bond is stronger in the proton transferred (PT) forms. In order to estimate the dimers' stabilization and forces responsible for it, the Symmetry-Adapted Perturbation Theory (SAPT) was applied. The energy decomposition revealed that dispersion is the primary factor stabilizing the dimeric forms and crystal structure of both compounds. The CPMD results showed that the proton transfer phenomena occurred in both studied compounds, as well as in both phases. In the case of compound 2, the proton transfer events are more frequent in the solid state, indicating an influence of the environmental effects on the bridged proton dynamics. Finally, the vibrational signatures were computed for both compounds using the CPMD trajectories. The Fourier transformation of the autocorrelation function of atomic velocity was applied to obtain the power spectra. The IR spectra show very broad absorption regions between 700 cm-1-1700 cm-1 and 2300 cm-1-3400 cm-1 in the gas phase and 600 cm-1-1800 cm-1 and 2200 cm-1-3400 cm-1 in the solid state for compound 1. The absorption regions for compound 2 were found as follows: 700 cm-1-1700 cm-1 and 2300 cm-1-3300 cm-1 for the gas phase and one broad absorption region in the solid state between 700 cm-1 and 3100 cm-1. The obtained spectroscopic features confirmed a strong mobility of the bridged protons. The inclusion of nuclear quantum effects showed a stronger delocalization of the bridged protons.

s-Triazine: A Privileged Structure for Drug Discovery and Bioconjugation

This review provides an overview of the broad applicability of s-triazine. Our many years working with this intriguing moiety allow us to discuss its wide activity spectrum (inhibition against MAO-A and -B, anticancer/antiproliferative and antimicrobial activity, antibacterial activity against MDR clinical isolates, antileishmanial agent, and use as drug nano delivery system). Most of the compounds addressed in our studies and those performed by other groups contain only N-substitution. Exploiting the concept of orthogonal chemoselectivity, first described by our group, we have successfully incorporated different nucleophiles in different orders into s-triazine core for application in peptides/proteins at a temperature compatible with biological systems.

Hydrogen bond system generated by nitroamino rearrangement: new character for designing next generation energetic materials

Hydrogen bond systems stabilize molecules and shorten intermolecular distances to give higher density and lower sensitivity.

Functionalization of Silica with Triazine Hydrazide to Improve Corrosion Protection and Interfacial Adhesion Properties of Epoxy Coating and Steel Substrate

The chemical bonding of modified filler surfaces with coating networks is an advanced approach for improving the interfacial adhesion force of fillers with coating and substrate surfaces. In this respect, silica gel surfaces were activated and modified by grafting 1,3–dihydrazide-2,4,6-triazine onto hydroxyl groups of activated silica surfaces. The chemical structure, thermal stability and surface morphologies of the modified silica were investigated. The modified silica fillers were blended during the curing of the epoxy resin with the polyamine hardener. The data regarding the chemical structure and thermal stability of the cured epoxy networks in the presence of modified silica elucidated the chemical bonding of amine groups on the silica surfaces cured with the oxirane epoxy resin. Moreover, the incorporation of modified silica in surfaces with epoxy networks improved their adhesion with steel surfaces and enhanced the mechanical, thermal and anticorrosion characteristics of the epoxy to protect steel surfaces against seawater.

Phenol as a Modulator in the Chemical Reactivity of 2,4,6-Trichloro-1,3,5-triazine: Rules of the Game II

2,4,6-Trichloro-1,3,5-triazine (TCT) is a privileged core that has the capacity to undergo sequential nucleophilic substitution reactions. Three nucleophiles, namely phenol, thiol and amine, were studied and the preferential order of incorporation on TCT was found to be first phenol, second thiol and third amine. The introduction of phenol was achieved at −20°C. The incorporation of this nucleophile in TCT helped to replace the third ‘Cl’ at 35°C, which is compatible with a biological context. The atomic charges on ‘Cl’ calculated by theoretical approaches were consistent with the experimental findings.

Energetic Butterfly: Heat-Resistant Diaminodinitro trans-Bimane

Due to a significant and prolific activity in the field of design and synthesis of new energetic molecules, it becomes increasingly difficult to introduce new explosophore structures with attractive properties. In this work, we synthesized a trans-bimane-based energetic material—3,7-diamino-2,6-dinitro-1H,5H-pyrazolo-[1,2-a]pyrazole-1,5-dione (4), the structure of which was comprehensively analyzed by a variety of advanced spectroscopic methods and by X-ray crystallo-graphy (with density of 1.845 g·cm⁻³ at 173 K). Although obtained crystals of 4 contained solvent molecules in their structure, state-of-the-art density functional theory (DFT) computational techniques allowed us to predict that solvent-free crystals of this explosive would preserve a similar tightly packed planar layered molecular arrangement, with the same number of molecules of 4 per unit cell, but with a smaller unit cell volume and therefore higher energy density. Explosive 4 was found to be heat resistant, with an onset decomposition temperature of 328.8 °C, and was calculated to exhibit velocity of detonation in a range of 6.88–7.14 km·s⁻¹ and detonation pressure in the range of 19.14–22.04 GPa, using for comparison both HASEM and the EXPLO 5 software. Our results indicate that the trans-bimane explosophore could be a viable platform for the development of new thermostable energetic materials.

Investigating Triorthogonal Chemoselectivity. Effect of Azide Substitution on the Triazine Core

An example of triorthogonal chemoselectivity is reported here for the first time. In this regard, a series of 43 reactions were performed using tridentate s-triazine as a model. In all of the possible cases, the three substitutions were carried out using different nucleophiles at a temperature compatible with biological systems.